A yellow ribbon tied around a tree in the Forest of Dean, Gloucestershire, one of the the country's heritage woodlands which may be affected by the government's plans. Photograph: Tim Ireland/PA

When I started my career in conservation in the mid-1980s, the Forestry Commission was environmental enemy number one. At that time it was using tax incentives and grants to promote large-scale commercial forestry expansion, including across large areas of peatlands in northern Scotland. The drainage of the vast Flow Country wilderness of Sutherland and Caithness became an environmental cause celebre.

How times have changed. Because of the campaigns run during the 1980s by groups including the RSPB and Friends of the Earth, the Forestry Commission changed. Many of the grants and incentives available these days reflect a deep change of emphasis. It's by no means perfect but the Forestry Commission today is a far more balanced agency.

The ecologically unique Brecklands of the Suffolk-Norfolk border was once a centre for Neolithic flint mining (Grimes Graves is here). The land was subsequently exhausted by grazing and rabbit warrens to become agriculturally unproductive heathland. After the first world war this "wasteland" was designated for forestry and subsequently became the largest area of lowland pine forests in these islands.

While for decades the forest was managed for commercial timber production, recent careful management has achieve some very positive outcomes for conservation. There are now several hundred pairs of breeding nightjar, and also several hundred pairs of the rare woodlark. It is the best place I know to see crossbills. Woodcock fly their wonderful summer evening displays, and there is always the chance of seeing a goshawk. These shy predators are evidently reassured by the vastness of the woods situated in the otherwise crowded south of England.

The plantlife is also remarkable. On one little patch of heath and grassland called Santon Warren, more than 40% of all the plants found in Britain have been recorded. A plethora of rare insects are found here too. Although this little corner of the forest park is free of trees, it is still run by the Forestry Commission and carefully grazed through a partnership with the Norfolk Wildlife Trust.

Even if you don't pay too much attention to wildlife, it is obvious the place is special. It is the nearest thing you will find in the British Isles to a continental steppe habitat. A feeling of remote wildness is preserved, and it is highly accessible through a network of cycling and hiking trails.

The cost of all this for taxpayers is minimal. Money made from commercial timber production is invested back into conservation and access for public enjoyment. The situation in Thetford Forests underlines the neatness of the arrangements that now prevail across so much of the English forest estate. It makes me wonder why ministers are so hell-bent on selling these lands into the private sector. They say it is to raise or save money, to avoid a conflict of interest (because the Forestry Commission is both a regulator and a doer), or because better outcomes can be achieved by private owners.

I have grave doubts as to how much money we will save. If forest land is transferred to commercial interests, wildlife and access for public enjoyment will not be priorities. Keeping those things would require financial incentives and the taxpayer would be the most likely source. As for conflict of interest, the opposite is true as we see how integrated land use can be achieved in practice. When it comes to the efficiencies that can be achieved by the private sector, sure they might make money, but whether the profitability of timber firms will reflect the public interest in conservation and enjoyment is a less certain outcome. The more I think about it, the more it seems that ideology has got ahead of common sense.

All political parties are founded on ideology, and that is part of what we vote for in elections. When ideology becomes dogmatic, however, we should pause for reflection. Political philosophy tends to thrive when it is the equal partner of common sense and practicality. If these essential elements are divorced then ideology can become self-defeating and society the casualty. Let's hope ministers will be brave enough to acknowledge this basic fact of politics, and to take a fresh look at what they are doing – before it is too late.